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(7×2 la purerea 2 +7 la puterea 2 × 2 la puterea 3):21

Răspuns :

(7×2² +7² × 2³):21 =
=7(2² +7 × 2³):(7×3) =
=(2² +7 × 2³):3 =
=2²×(1 +7 × 2):3=
=2²×15:3=
=2²×5=20




=(7×4+49×8)÷21=
=(28+392)÷21=
=420÷21=20